The invention relates to a measuring device for determining an absolute position of a movable element, comprising a scale graduation element with a number of tracks and a pick-up device which comprises a number of sensing elements which corresponds to the number of tracks, said sensing elements being provided with sensors and said tracks including an incremental track and an absolute track and being formed as a succession of strip-shaped parts, each of which has a property which can be detected by the sensors and which is dependent on the location on the scale graduation element, and also comprising a signal processing system for determining the absolute position of the movable element from a combination of, on the one hand, signals originating from the sensors of the sensing element associated with the absolute track and, on the other hand, signals originating from the sensors of the sensing element associated with the incremental track.
The invention also relates to a scale graduation element suitable for use in such a measuring device.
A measuring device of this kind is known from European Patent Application EP 0 246 404 A2. The cited Application describes a measuring device for determining the relative position of two objects, utilizing a scale graduation element in the form of a measuring ruler on which there are provided on the one hand an incremental graduation and on the other hand a graduation of reference marks whereto an absolute position is assigned. This has a drawback in that it is not possible to determine the absolute position without displacing the pick-up device at least as far as the next absolute reference mark. The sensing of the incremental track produces an absolute measure within a pitch, but the resolution of the determination of the absolute value on the measuring ruler is limited by the encoding of the reference marks and the minimum distance that can be achieved between these marks.